In the recent years, vibration countermeasures for various kinds of equipment are in demand, and especially, vibration countermeasures are needed in fields such as automobiles, domestic electric appliances, and precision instruments. In general, materials having high vibration-damping properties include composite materials such as materials in which a metal plate is pasted with a vibration-absorbable material such as a rubber and asphalt, a vibration damping steel plate in which a vibration-absorbable material is interposed between metal plates. These vibration-damping materials retain their shapes with a high-rigidity metal plate and absorb vibrations with a vibration-absorbable material. Also, in a case of metals alone, a vibration-damping material includes an alloy material that absorbs vibrations by converting kinetic energy to thermal energy utilizing twinning or ferromagnetic property. However, there were some disadvantages that since composite materials paste together different materials, there are limitations in mold processability, and also that a metal steel plate is used, so that the manufactured article itself becomes heavy.
In addition, the alloy material was heavy because only metals were used, and further it was insufficient in vibration-damping properties.
In view of the prior art as mentioned above, as a functional resin composition that has a vibration-damping function, for example, Patent Publication 1 discloses a sound insulation material constructed from a polyamide resin, a plasticizer in an amount of from 5 to 40 parts by weight, and reinforcing fibers in an amount of from 10 to 70 parts by weight, based on 100 parts by weight of the polyamide resin. Here, the publication describes that as a reinforcing material, reinforcing fibers such as glass fibers, aramid fibers, carbon fibers, and whiskers are used, but also a filler such as iron oxide, alumina, or zinc oxide can be used in combination.
In addition, Patent Publication 2 discloses that vibration-damping property and flowability are largely improved by blending a polyamide resin with a polyamide monomer and/or a nonamer or lower polyamide oligomer in a specified amount. It is possible to blend a plasticizer or an inorganic filler to the above composition, and 45 parts by weight of glass fibers are blended based on 100 parts by weight of the resin in Examples.
Patent Publication 1: Japanese Patent Laid-Open No. Hei-4-89863
Patent Publication 2: Japanese Patent Laid-Open No. 2006-70154